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Experimental and theoretical investigation of backward-facing step flow

Published online by Cambridge University Press:  20 April 2006

B. F. Armaly ,
F. Durst ,
J. C. F. Pereira  and
B. Schönung
B. F. Armaly
Affiliation:
Institute of Hydromechanics, Section III: Mechanics of Turbulent Flows, University of Karlsruhe, Kaiserstraße 12, D-7500 Karlsruhe, F.R.G. Present address: Mechanical Engineering Department, University of Missouri-Rolla, Rolla, Missouri 65401, U.S.A.
F. Durst
Affiliation:
Institute of Hydromechanics, Section III: Mechanics of Turbulent Flows, University of Karlsruhe, Kaiserstraße 12, D-7500 Karlsruhe, F.R.G. Present address: Lehrstuhl für Strömungslehre, Universität Erlangen-Nürnberg, Egerlandstraße 13, D-8520 Erlangen, F.R.G.
J. C. F. Pereira
Affiliation:
Institute of Hydromechanics, Section III: Mechanics of Turbulent Flows, University of Karlsruhe, Kaiserstraße 12, D-7500 Karlsruhe, F.R.G.
B. Schönung
Affiliation:
Institute of Hydromechanics, Section III: Mechanics of Turbulent Flows, University of Karlsruhe, Kaiserstraße 12, D-7500 Karlsruhe, F.R.G.
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Abstract

Laser-Doppler measurements of velocity distribution and reattachment length are reported downstream of a single backward-facing step mounted in a two-dimensional channel. Results are presented for laminar, transitional and turbulent flow of air in a Reynolds-number range of 70 < Re < 8000. The experimental results show that the various flow regimes are characterized by typical variations of the separation length with Reynolds number. The reported laser-Doppler measurements do not only yield the expected primary zone of recirculating flow attached to the backward-facing step but also show additional regions of flow separation downstream of the step and on both sides of the channel test section. These additional separation regions have not been previously reported in the literature.

Although the high aspect ratio of the test section (1:36) ensured that the oncoming flow was fully developed and two-dimensional, the experiments showed that the flow downstream of the step only remained two-dimensional at low and high Reynolds numbers.

The present study also included numerical predictions of backward-facing step flow. The two-dimensional steady differential equations for conservation of mass and momentum were solved. Results are reported and are compared with experiments for those Reynolds numbers for which the flow maintained its two-dimensionality in the experiments. Under these circumstances, good agreement between experimental and numerical results is obtained.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 127 , February 1983 , pp. 473 - 496
Copyright
© 1983 Cambridge University Press

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